<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<button onclick="f1()">点击</button>
<select name="mon" id="month">
    <option value=""></option>
</select>
</body>
    <script>
        function f1() {
            var moth = ["一月","二月","三月","四月","五月","六月","七月","八月","九月","十月","十一月"]
            var m = document.getElementById("month");
            m.options.length=0;
            for (var i = 0; i < moth.length; i++) {
                var n = moth[i];
                var op = new Option(n,i);
                m.add(op);
            }
            var date = new Date();
            m.value=date.getMonth();
        }
    </script>
</html>